(a) Field of the Invention
This invention relates to an albada finder improved so that images within the visual field can be well seen.
(b) Description of the Prior Art
In the conventional albada finder, mostly the astigmatism is generated to be so large that the sight of the visual field is bad and particularly the sight of the periphery of the visual field has been bad. Further, in incorporating a range finder or the like into the albada finder, it is desirable to place a half mirror between the reflecting surface and the surface on which the field mask is provided of the objective. However, in the albada finder in which the half mirror is thus placed between the reflecting surface and the surface on which the field mask is provided, the field mask image is likely to become dark. In order to improve it to make the field mask image bright, it is considered to make the surface on which the field mask is provided spherical as shown in FIG. 1 so that the light will be easy to collect. However, in case the surface on which the field mask is provided is thus made spherical, the astigmatism will be more generated.